1. Field of the Invention
The present invention relates to a method of manufacturing a magnetic head for perpendicular magnetic recording that is used for writing data on a recording medium by means of a perpendicular magnetic recording system.
2. Description of the Related Art
The recording systems of magnetic read/write apparatuses include a longitudinal magnetic recording system wherein signals are magnetized in a direction along the plane of the recording medium (the longitudinal direction) and a perpendicular magnetic recording system wherein signals are magnetized in a direction perpendicular to the plane of the recording medium. It is known that the perpendicular magnetic recording system is harder to be affected by thermal fluctuation of the recording medium and capable of providing higher linear recording density, compared with the longitudinal magnetic recording system.
Like magnetic heads for longitudinal magnetic recording, those for perpendicular magnetic recording typically have a structure in which a read head including a magnetoresistive element (hereinafter, also referred to as an MR element) for reading and a write head including an induction-type electromagnetic transducer for writing are stacked on a substrate. The write head includes a pole layer that produces a magnetic field in the direction perpendicular to the plane of the recording medium. The pole layer includes, for example, a track width defining portion having an end located in a medium facing surface that faces the recording medium, and a wide portion that is coupled to the other end of the track width defining portion and that is greater in width than the track width defining portion. The track width defining portion has a nearly uniform width. To achieve a higher recording density, a reduction in track width and an improvement in write characteristics, such as an overwrite property that is a parameter indicating an overwriting capability, are required of the write head of the perpendicular magnetic recording system.
As a magnetic head for perpendicular magnetic recording, there is known a magnetic head including a shield that has an end face located in the medium facing surface at a position forward of the end face of the pole layer along the direction of travel of the recording medium with a predetermined distance provided therebetween, as disclosed in U.S. Patent Application Publication No. 2005/0219747 A1, for example. A gap layer made of a nonmagnetic material is provided between the pole layer and the shield. The shield has the function of preventing a magnetic flux from reaching the recording medium, the magnetic flux being generated from the end face of the pole layer and expanding in directions except the direction perpendicular to the plane of the recording medium. A magnetic head including such a shield enables a further improvement in recording density.
A magnetic head for use in a magnetic disk drive such as a hard disk drive is typically provided in a slider. The slider has the medium facing surface mentioned above. The medium facing surface has an air-inflow-side end and an air-outflow-side end. The slider is configured to slightly fly over the surface of the recording medium by means of an airflow that comes from the air-inflow-side end into the space between the medium facing surface and the recording medium. The magnetic head is typically disposed near the air-outflow-side end of the medium facing surface of the slider. In a magnetic disk drive, the magnetic head is aligned through the use of a rotary actuator, for example. In this case, the magnetic head moves over the recording medium along a circular orbit about the center of rotation of the rotary actuator. In such a magnetic disk drive, a tilt of the magnetic head with respect to the tangent of the circular track, which is called a skew, occurs in accordance with the position of the magnetic head across the tracks.
In a magnetic disk drive of the perpendicular magnetic recording system, in particular, which exhibits a better capability of writing on a recording medium compared with the longitudinal magnetic recording system, the skew mentioned above often causes a phenomenon in which, when data is written on a certain track, data stored on a track adjacent thereto is erased (this phenomenon is hereinafter called adjacent track erasing). To achieve a higher recording density, it is required to suppress the adjacent track erasing.
As a technique for suppressing the adjacent track erasing resulting from the skew mentioned above, it is effective to form a tapered surface in the top surface of the pole layer near the medium facing surface such that the thickness of the pole layer near the medium facing surface decreases toward the medium facing surface, as disclosed in U.S. Patent Application Publication No. 2005/0219747 A1. This technique allows a reduction in thickness of the track width defining portion in the medium facing surface, thereby making it possible to suppress the adjacent track erasing resulting from the skew. This technique also allows guiding a magnetic flux of great magnitude to the medium facing surface through the pole layer, thereby making it possible to suppress degradation of the write characteristics (overwrite property).
As a technique for suppressing the adjacent track erasing in a write head of the perpendicular magnetic recording system, it is also effective to provide two side shields on both sides of the pole layer that are opposite to each other in the track width direction, as disclosed in U.S. Patent Application Publication No. 2007/0177301 A1. A magnetic head including such two side shields allows suppression of the adjacent track erasing because it is possible to take in a magnetic flux that is generated from the end face of the pole layer and extends in the track width direction.
In a magnetic head including two side shields, flux leakage from the pole layer to the two side shields can often occur since the two side shields are present near the pole layer. The relative locations of the pole layer and the two side shields and the shapes of the pole layer and the two side shields therefore influence the write characteristics. To achieve desired write characteristics, it is thus important to accurately align the pole layer and the two side shields with respect to each other and to control the respective shapes of the pole layer and the two side shields.
Typically, the pole layer and the two side shields are patterned using different masks. In this case, it is difficult to accurately align the pole layer and the two side shields with respect to each other.
U.S. Patent Application Publication No. 2007/0211377 A1 discloses a method of forming a groove for accommodating the pole layer and two grooves for accommodating the two side shields simultaneously in a nonmagnetic layer by etching through the use of a single mask. This method allows accurate alignment of the pole layer and the two side shields with respect to each other. According to this method, however, since the groove for accommodating the pole layer and the two grooves for accommodating the two side shields are formed simultaneously, it is difficult to control the shape of the groove for accommodating the pole layer and the shapes of the two grooves for accommodating the two side shields independently of each other. Consequently, it is difficult with this method to control the respective shapes of the pole layer and the two side shields into desired shapes. It is also impossible with this method to reduce the distance between the pole layer and each of the two side shields beyond the limit that can be defined by the mask.